U.S. patent application number 11/751989 was filed with the patent office on 2007-11-29 for alkaline storage battery.
This patent application is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Takashi Asahina, Toyohiko Eto, Shinji Hamada, Masanori Ito.
Application Number | 20070275301 11/751989 |
Document ID | / |
Family ID | 38749921 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070275301 |
Kind Code |
A1 |
Asahina; Takashi ; et
al. |
November 29, 2007 |
ALKALINE STORAGE BATTERY
Abstract
An alkaline storage battery has an electrode terminal that is
inserted in a penetration hole, and disposed astride an inside of a
battery case and an outside of the battery case, and fastened to a
hole periphery portion via a packing. The negative terminal has a
seal portion that, together with the hole periphery portion, clamps
and compresses the packing to liquid-tightly seal the penetration
hole. The seal portion includes an annular seal surface located
facing the hole periphery portion, and a seal periphery surface
located around the seal surface. The seal surface is protruded from
the seal periphery surface toward the hole periphery portion. The
surface roughness Ry of the seal surface of the negative terminal
is 15 .mu.m or less.
Inventors: |
Asahina; Takashi;
(Toyohashi-shi, JP) ; Hamada; Shinji;
(Toyohashi-shi, JP) ; Eto; Toyohiko; (Toyota-shi,
JP) ; Ito; Masanori; (Toyohashi-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Toyota Jidosha Kabushiki
Kaisha
Toyota-shi
JP
|
Family ID: |
38749921 |
Appl. No.: |
11/751989 |
Filed: |
May 22, 2007 |
Current U.S.
Class: |
429/181 ;
429/185 |
Current CPC
Class: |
H01M 50/166 20210101;
H01M 50/172 20210101; H01M 50/543 20210101; Y02E 60/10 20130101;
H01M 10/281 20130101 |
Class at
Publication: |
429/181 ;
429/185 |
International
Class: |
H01M 2/06 20060101
H01M002/06; H01M 2/08 20060101 H01M002/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2006 |
JP |
2006-143038 |
Claims
1. An alkaline storage battery comprising: a battery case that has
an external wall portion which has an inside surface and an outside
surface, and which includes a penetration hole penetrating between
the inside surface and the outside surface; an alkaline electrolyte
located in the battery case; a packing that intimately contacts a
hole periphery portion of the external wall portion that surrounds
the penetration hole; and an electrode terminal inserted in the
penetration hole, and disposed astride an inside of the battery
case and an outside of the battery case, and fastened to the hole
periphery portion via the packing, wherein the electrode terminal
has a seal portion that, together with the hole periphery portion,
clamps and compresses the packing to liquid-tightly seal the
penetration hole, and wherein the seal portion includes an annular
seal surface whose surface roughness Ry is 15 .mu.m or less and
which is located facing the hole periphery portion, and a seal
periphery surface located around the seal surface, and the seal
surface is protruded from the seal periphery surface toward the
hole periphery portion.
2. The alkaline storage battery according to claim 1, wherein the
electrode terminal is formed by deep draw molding of a metal
sheet.
3. An alkaline storage battery comprising: a battery case that has
an external wall portion which has an inside surface and an outside
surface, and which includes a penetration hole penetrating between
the inside surface and the outside surface; an alkaline electrolyte
located in the battery case; a packing that intimately contacts a
hole periphery portion of the external wall portion that surrounds
the penetration hole; and an electrode terminal inserted in the
penetration hole, and disposed astride an inside of the battery
case and an outside of the battery case, and fastened to the hole
periphery portion via the packing, wherein the electrode terminal
has a seal portion that is formed by press molding of a metal
sheet, and that, together with the hole periphery portion, clamps
and compresses the packing to liquid-tightly seal the penetration
hole, and wherein the seal portion includes an annular seal surface
that is located facing the hole periphery portion, and that is
subjected to a surface roughness reducing process through
pressurization surface correction during or after the molding of
the seal portion, and a seal periphery surface located around the
seal surface, and the seal surface is protruded from the seal
periphery surface toward the hole periphery portion.
4. The alkaline storage battery according to claim 3, wherein the
electrode terminal is formed by deep draw molding of a metal
sheet.
5. An alkaline storage battery comprising: a battery case that has
an external wall portion which has an inside surface and an outside
surface, and which includes a penetration hole penetrating between
the inside surface and the outside surface; an alkaline electrolyte
located in the battery case; a packing that intimately contacts a
hole periphery portion of the external wall portion that surrounds
the penetration hole; and an electrode terminal inserted in the
penetration hole, and disposed astride an inside of the battery
case and an outside of the battery case, and fastened to the hole
periphery portion via the packing, wherein the electrode terminal
has a seal portion that is formed by press molding of a metal
sheet, and that, together with the hole periphery portion, clamps
and compresses the packing to liquid-tightly seal the penetration
hole, and wherein the seal portion includes an annular seal surface
that is located facing the hole periphery portion, and that is
ground after the molding of the seal portion, and a seal periphery
surface located around the seal surface, and the seal surface is
protruded from the seal periphery surface toward the hole periphery
portion.
6. The alkaline storage battery according to claim 5, wherein the
electrode terminal is formed by deep draw molding of a metal
sheet.
7. An alkaline storage battery comprising: a battery case that has
an external wall portion which has an inside surface and an outside
surface, and which includes a penetration hole penetrating between
the inside surface and the outside surface; a packing that
intimately contacts a hole periphery portion of the external wall
portion that surrounds the penetration hole; an electrode terminal
inserted in the penetration hole, and disposed astride an inside of
the battery case and an outside of the battery case, and fastened
to the hole periphery portion via the packing; and an alkaline
electrolyte located in the battery case, wherein the electrode
terminal has a seal portion that is formed by press molding of a
metal sheet containing iron as a main component, and that, together
with the hole periphery portion, clamps and compresses the packing
to liquid-tightly seal the penetration hole, and wherein the seal
portion includes an annular seal surface that is located facing the
hole periphery portion, and that is made of a nickel plating layer
provided after the molding of the seal portion, and a seal
periphery surface located around the seal surface, and the seal
surface is protruded from the seal periphery surface toward the
hole periphery portion.
8. The alkaline storage battery according to claim 7, wherein in
the seal portion, a coated surface that is coated with the nickel
plating layer that forms the seal surface is subjected to a surface
roughness reducing process through pressurization surface
correction during or after the molding of the seal portion.
9. The alkaline storage battery according to claim 7, wherein in
the seal portion, a coated surface that is coated with the nickel
plating layer that forms the seal surface is ground after the
molding of the seal portion.
10. The alkaline storage battery according to claim 8, wherein the
electrode terminal is formed by deep draw molding of a metal sheet
containing iron as a main component.
11. The alkaline storage battery according to claim 9, wherein the
electrode terminal is formed by deep draw molding of a metal sheet
containing iron as a main component.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2006-143038 filed on May 23, 2006, including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The invention relates to an alkaline storage battery.
[0004] 2. Description of Related Art
[0005] In recent years, various alkaline storage batteries have
been developed. For example, Japanese Patent Application
Publication No. JP-A-2001-313066 discloses an alkaline storage
battery in which an electrode body formed by alternately stacking a
plurality of positive plates and a plurality of negative plates
with one separator disposed between every two plates is housed in a
rectangular parallelepiped-shape battery case. This alkaline
storage battery has electrode terminals (a positive terminal and a
negative terminal) that are disposed astride the inside and the
outside of the case through penetration holes penetrating a lid of
the case.
[0006] In the alkaline storage batteries, due to the use of an
alkaline electrolyte, a so-called electrolyte solution creep
phenomenon occurs in which the electrolyte solution in the case
creeps up the surfaces of the electrode terminals. This phenomenon
is remarkable particularly in the negative terminal. Therefore, in
the alkaline storage battery shown in Japanese Patent Application
Publication No. JP-A-2001-313066, if the sealing of a penetration
hole in which an electrode terminal is inserted is not sufficient,
the electrolyte solution may leak out along the surfaces of the
electrode terminals after a long time of use due to the creep
phenomenon of the electrolyte solution.
[0007] Japanese Patent Application Publication No. JP-A-2003-272589
discloses a closed-type alkaline storage battery that has good seal
characteristic, and restrains the seepage of the electrolyte
solution from inside the battery, and operates a safety valve
appropriately. In this closed type alkaline storage battery, in
order to prevent leakage of the electrolyte solution via the safety
valve, a surface roughness Ra is prescribed regarding a region in
an opening closure plate which contacts a protection portion of the
valve body. However, the surface roughness Ra, being an
representation of an arithmetic average from an average line of a
roughness curve, is not suitable to prescribe the surface roughness
of a seal portion of an electrode terminal (a site that prevents
the alkaline electrolyte from leaking out along the surfaces of the
electrode terminal) that has undergone complicated forming (deep
draw molding or the like). A reason therefor is that an electrode
terminal having undergone complicated molding (deep draw molding or
the like) may sometimes have local roughening of the surface of the
seal portion to great extent due to occurrence of cracks and the
like, and in such a case, the alkaline electrolyte may leak out via
a site where cracks or the like occur, even if the value of Ra is
small.
SUMMARY OF THE INVENTION
[0008] It is an object of the invention to provide an alkaline
storage battery in which the leakage of the electrolyte solution to
the outside along the surfaces of the electrode terminals is
restrained.
[0009] A first aspect of the invention relates to an alkaline
storage battery. This alkaline storage battery includes: a battery
case that has an external wall portion which has an inside surface
and an outside surface, and which includes a penetration hole
penetrating between the inside surface and the outside surface; a
packing that intimately contacts a hole periphery portion of the
external wall portion that surrounds the penetration hole; an
electrode terminal inserted in the penetration hole, and disposed
astride an inside of the battery case and an outside of the battery
case, and fastened to the hole periphery portion via the packing,
the electrode terminal having a seal portion that, together with
the hole periphery portion, clamps and compresses the packing to
liquid-tightly seal the penetration hole, the seal portion
including an annular seal surface located facing the hole periphery
portion, and a seal periphery surface located around the seal
surface, and the seal surface being protruded from the seal
periphery surface toward the hole periphery portion; and an
alkaline electrolyte located in the battery case. In this alkaline
storage battery, a surface roughness Ry of the seal surface of the
electrode terminal is 15 .mu.m or less.
[0010] The electrode terminal of the alkaline storage battery in
accordance with the first aspect has a seal portion that cramps and
compresses the packing in cooperation with the hole periphery
portion surrounding the penetration hole in the external wall
portion so that the packing liquid-tightly seals the penetration
hole. The seal portion has a seal surface that is protruded from
the seal periphery surface toward the hole periphery portion.
Therefore, particularly on the seal surface, the packing can be
locally compressed to liquid-tightly seal the penetration hole.
[0011] If the surface roughness of the seal surface of the
electrode terminal is large (if the surface is rough), the liquid
tightness for the electrolyte solution between the seal surface and
the packing becomes insufficient. In such a case, due to the creep
phenomenon of the alkaline electrolyte on the electrode terminal,
the alkaline electrolyte will likely leak out along the surfaces of
the electrode terminal.
[0012] However, in the alkaline storage battery in accordance with
the first aspect of the invention, the surface roughness Ry of the
seal surface of the electrode terminal is 15 .mu.m or less. By
keeping small the surface roughness of the electrode terminal in
this manner, the liquid tightness for the electrolyte solution
between the seal surface and the packing becomes good, so that the
leakage of the alkaline electrolyte to the outside along the
surfaces of the electrode terminal can be restrained. Incidentally,
the surface roughness Ry is a parameter that indicates the surface
roughness defined in JIS B 0601 and JIS B 0031. The value Ry,
unlike the value Ra, represents the difference between a peak line
and a trough line of the roughness curve (maximum height).
Therefore, even in the case where the electrode terminal is molded
by a complicated molding process (deep draw molding or the like)
that is likely to cause cracks, the surface roughness of the seal
surface can be appropriately evaluated against the leakage of the
alkaline electrolyte.
[0013] A second aspect of the invention relates to an alkaline
storage battery. This alkaline storage battery includes: a battery
case that has an external wall portion which has an inside surface
and an outside surface, and which includes a penetration hole
penetrating between the inside surface and the outside surface; a
packing that intimately contacts a hole periphery portion of the
external wall portion that surrounds the penetration hole; an
electrode terminal inserted in the penetration hole, and disposed
astride an inside of the battery case and an outside of the battery
case, and fastened to the hole periphery portion via the packing,
the electrode terminal having a seal portion that, together with
the hole periphery portion, clamps and compresses the packing to
liquid-tightly seal the penetration hole, the seal portion
including an annular seal surface located facing the hole periphery
portion, and a seal periphery surface located around the seal
surface, and the seal surface being protruded from the seal
periphery surface toward the hole periphery portion; and an
alkaline electrolyte located in the battery case. In the electrode
terminal, at least the seal portion is formed by press molding of a
metal sheet, and the seal surface of the seal portion is subjected
to a surface roughness reducing process through pressurization
surface correction during or after the molding of the seal
portion.
[0014] In the alkaline storage battery in accordance with the
second aspect of the invention, at least the seal portion of the
electrode terminal is formed by press-molding a metal sheet.
Incidentally, there are cases where the entire or a portion of the
seal surface of the seal portion remains out of contact with the
die when the seal portion is formed by press-molding a metal sheet.
In such a case, the surface roughness of the seal surface becomes
large (the surface becomes rough), so that the liquid tightness for
the electrolyte solution between the seal surface and the packing
may sometimes become insufficient.
[0015] However, in the alkaline storage battery in accordance with
the second aspect of the invention, the seal surface of the seal
portion is subjected to the surface roughness reducing process
through pressurization surface correction during or after the
molding of the seal portion. This reduces the surface roughness of
the seal surface of the seal portion, so that good liquid tightness
for the electrolyte solution between the seal surface and the
packing can be achieved. Therefore, the leakage of the alkaline
electrolyte to the outside along the surfaces of the electrode
terminal can be restrained.
[0016] The surface roughness reducing process through
pressurization surface correction during the molding of the seal
portion refers to a process in which during the molding of the seal
portion, through the use of a die having such a configuration that
the seal surface contacts a contact surface of the die, and is
molded in accordance with the shape of the contact surface, the
seal surface is molded on the contact surface of the die while
being pressed against the contact surface. The surface roughness
reducing process through pressurization surface correction after
the molding of the seal portion refers to a process in which after
the seal portion is molded, the seal surface is pressed against the
contact surface of the die for correction of the surface.
[0017] A third aspect of the invention relates to an alkaline
storage battery. This alkaline storage battery includes: a battery
case that has an external wall portion which has an inside surface
and an outside surface, and which includes a penetration hole
penetrating between the inside surface and the outside surface; a
packing that intimately contacts a hole periphery portion of the
external wall portion that surrounds the penetration hole; an
electrode terminal inserted in the penetration hole, and disposed
astride an inside of the battery case and an outside of the battery
case, and fastened to the hole periphery portion via the packing,
the electrode terminal having a seal portion that together with the
hole periphery portion, clamps and compresses the packing to
liquid-tightly seal the penetration hole, the seal portion
including an annular seal surface located facing the hole periphery
portion, and a seal periphery surface located around the seal
surface, and the seal surface being protruded from the seal
periphery surface toward the hole periphery portion; and an
alkaline electrolyte located in the battery case. In the electrode
terminal, at least the seal portion is formed by the press molding
of a metal sheet, and the seal surface of the seal portion is
ground after the molding of the seal portion.
[0018] In the alkaline storage battery of the third aspect of the
invention, the seal surface of the seal portion of the electrode
terminal is ground after the seal portion has been molded. This
reduces the surface roughness of the seal surface of the seal
portion, so that good liquid tightness for the electrolyte solution
between the seal surface and the packing can be achieved.
Therefore, the leakage of the alkaline electrolyte to the outside
along the surfaces of the electrode terminal can be restrained.
Incidentally, the grinding of the seal surface is also an aspect of
the surface roughness reducing process in the invention. Examples
of the grinding of the seal surface include barrel plating, buff
grinding, etc.
[0019] In the alkaline storage battery in accordance with any one
of the first to third aspects of the invention, the surface
roughness Ry of the seal surface of the electrode terminal may be
15 .mu.m or less. If the surface roughness of the seal surface of
the electrode terminal is reduced to 15 .mu.m or less, good liquid
tightness for the electrolyte solution between the seal surface and
the packing is achieved, so that the leakage of the alkaline
electrolyte to the outside along the surfaces of the electrode
terminal can be restrained.
[0020] The electrode terminal of the alkaline storage battery in
accordance with any one of the first to third aspects of the
invention may be formed by deep draw molding of a metal sheet.
[0021] In the alkaline storage battery in accordance with any one
of the first to third aspects of the invention, the electrode
terminal is formed by the deep draw molding of a metal sheet. In
the case of the electrode terminal is deep-draw-molded, the surface
roughness of the seal surface of the seal portion, in particular,
is likely to become rough at the time of molding. Furthermore, the
seal surface may sometimes locally become rough to great extent due
to occurrence of cracks or the like. In such a case, the alkaline
electrolyte sometimes leak out through the site of rough surface
even if the value of the surface roughness Ra of the seal surface
is small.
[0022] However, in the alkaline storage battery in accordance with
any one of the first to third aspects of the invention, the value
Ry representing the difference (maximum height) between a peak line
and a trough line of the roughness curve is used as parameter that
indicates the surface roughness of the seal surface of the
electrode terminal, and the surface roughness Ry of the seal
surface is prescribed to be 15 .mu.m or less. Therefore, although
the electrode terminal formed by deep draw molding is used, good
liquid tightness for the electrolyte solution between the seal
surface and the packing can be achieved, so that the leakage of the
alkaline electrolyte to the outside along the surfaces of the
electrode terminal can be restrained. Furthermore, in the alkaline
storage battery in accordance with any one of the first to third
aspects of the invention, the seal surface is subjected to the
surface roughness reducing process through pressurization surface
correction or to the grinding. This reduces the surface roughness
of at least the seal surface, so that the leakage of the alkaline
electrolyte to the outside along the surfaces of the electrode
terminal can be restrained.
[0023] A fourth aspect of the invention relates to an alkaline
storage battery. This alkaline storage battery includes: a battery
case that has an external wall portion which has an inside surface
and an outside surface, and which includes a penetration hole
penetrating between the inside surface and the outside surface; a
packing that intimately contacts a hole periphery portion of the
external wall portion that surrounds the penetration hole; an
electrode terminal inserted in the penetration hole, and disposed
astride an inside of the battery case and an outside of the battery
case, and fastened to the hole periphery portion via the packing,
the electrode terminal having a seal portion that, together with
the hole periphery portion, clamps and compresses the packing to
liquid-tightly seal the penetration hole, the seal portion
including an annular seal surface located facing the hole periphery
portion, and a seal periphery surface located around the seal
surface, and the seal surface being protruded from the seal
periphery surface toward the hole periphery portion; and an
alkaline electrolyte located in the battery case. In the electrode
terminal, at least the seal portion is formed by press molding of a
metal sheet containing iron as a main component, and the seal
surface of the seal portion is made of a nickel plating layer
provided after the molding of the seal portion.
[0024] In the alkaline storage battery in accordance with the
fourth aspect of the invention, at least the seal portion of the
electrode terminal is formed by press-molding a metal sheet
containing iron as a main component. Incidentally, a phenomenon in
which the alkaline electrolyte leaks out along the surfaces of the
electrode terminal due to the creep phenomenon of the alkaline
electrolyte becomes likely to occur particularly if iron is exposed
in the seal surface of the electrode terminal. In the case where
the seal portion is formed by press-molding a steel sheet such as a
cold-rolled steel sheet, it is a matter of course that iron is
exposed in the seal surface. In the case where the seal portion is
formed by press-molding a nickel-plated steel sheet (a steel sheet
whose surface is plated with nickel), it also sometimes happen that
cranks or the like occur in the nickel plating of the seal surface
and iron is thus exposed in the seal surface.
[0025] However, in the alkaline storage battery in accordance with
the fourth aspect of the invention, the seal surface of the seal
portion is constructed of a nickel plating layer provided after the
molding of the seal portion. This prevents the exposure of iron in
the seal surface, so that the creep phenomenon of the alkaline
electrolyte on the seal surface can be restrained. Therefore, the
leakage of the alkaline electrolyte to the outside along the
surfaces of the electrode terminal can be restrained. Incidentally,
examples of the metal sheet containing iron as a main component
include cold-rolled steel sheets, such as SPCE or the like, a
nickel mesh steel sheet whose surface is plated with nickel.
[0026] In the seal portion of the alkaline storage battery, a
coated surface that is coated with the nickel plating layer that
forms the seal surface may be subjected to a surface roughness
reducing process through pressurization surface correction during
or after the molding of the seal portion.
[0027] In the alkaline storage battery in accordance with the
fourth aspect of the invention, the coated surface of the seal
portion is subjected to the surface roughness reducing process
through pressurization surface correction during or after the
molding of the seal portion. This reduces the surface roughness of
the coated surface, and therefore also reduces the surface
roughness of the seal surface constructed of the nickel plating
layer that coats the coated surface. Therefore, the leakage of the
alkaline electrolyte to the outside along the surfaces of the
electrode terminal can be further restrained.
[0028] In the seal portion of the alkaline storage battery in
accordance with the fourth aspect of the invention, the coated
surface that is coated with the nickel plating layer that forms the
seal surface may be ground after the molding of the seal
portion.
[0029] In such an alkaline storage battery, the coated surface of
the seal portion is ground after the molding of the seal portion.
This reduces the surface roughness of the coated surface, and
therefore also reduces the surface roughness of the seal surface
constructed of the nickel plating layer that coats the coated
surface. Therefore, the leakage of the alkaline electrolyte to the
outside along the surfaces of the electrode terminal can be further
restrained.
[0030] Furthermore, the electrode terminal of the alkaline storage
battery in accordance with the fourth aspect of the invention may
be formed by deep draw molding of a metal sheet containing iron as
a main component.
[0031] In the alkaline storage battery of the invention, the
electrode terminal is formed by the deep draw molding of a metal
sheet. In the case where the electrode terminal is
deep-draw-molded, the surface of the coated surface of the seal
portion (a surface coated with the nickel plating layer that
constitutes the seal surface) in particular is liable to become
rough. However, in the alkaline storage battery of the invention,
the coated surface is subjected to the surface roughness reducing
process through pressurization surface correction or to the
grinding as mentioned above. This reduces the surface roughness of
at least the coated surface, and therefore also reduces the surface
roughness of the seal surface constructed of the nickel plating
layer that coats the coated surface. Therefore, the leakage of the
alkaline electrolyte to the outside along the surfaces of the
electrode terminal can be restrained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The foregoing and further objects, features and advantages
of the invention will become apparent from the following
description of preferred embodiments with reference to the
accompanying drawings, wherein like numerals are used to represent
like elements and wherein:
[0033] FIG. 1 is a front view of an alkaline storage battery 100 to
500 in accordance with Embodiments 1 to 5;
[0034] FIG. 2 is a side view of the alkaline storage battery 100 to
500 in accordance with Embodiments 1 to 5;
[0035] FIG. 3 is a sectional view of the alkaline storage battery
100 in accordance with Embodiment 1, corresponding to a sectional
view taken on line III-III in FIG. 2;
[0036] FIG. 4 is an enlarged sectional view of a negative terminal
140;
[0037] FIG. 5 is an enlarged sectional view of a seal portion of
the negative terminal 140;
[0038] FIG. 6 is a perspective view of a negative terminal
substrate 14;
[0039] FIG. 7 is a diagram illustrating a surface roughness
reducing process;
[0040] FIG. 8 is a sectional view of a negative terminal member
140A to 340A (a negative terminal 140 to 340 before being attached
to a battery);
[0041] FIG. 9 is a sectional view of a negative terminal member
440A, 540A (a negative terminal 440, 540 before being attached to a
battery);
[0042] FIG. 10 is a graph indicating results of a leak test;
and
[0043] FIG. 11 is a graph indicating the surface roughnesses Ry of
seal surfaces.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Embodiments of the invention will now be described. This
embodiment will be described with reference to a nickel-metal
hydride storage battery as an example of the alkaline storage
battery. The leakage of an alkaline electrolyte along the surfaces
of an electrode terminal will be described regarding a negative
terminal on which the alkaline electrolyte creep phenomenon is
remarkable.
[0045] (Embodiment 1) FIG. 1 is a front view of an alkaline storage
battery 100 in accordance with Embodiment 1. FIG. 2 is a side view
thereof. FIG. 3 is a sectional view thereof (corresponding to a
sectional view taken along line III-III in FIG. 2). The alkaline
storage battery 100 in accordance with Embodiment 1 is a
square-shape closed type nickel-metal hydride storage battery that
includes a battery case 110 made of a metal (e.g., a nickel-plated
steel sheet), negative terminals 140, a safety valve 113, and an
electrode body 150 (see FIG. 3) and an alkaline electrolyte (not
shown) that are disposed within the battery case 110. The alkaline
electrolyte used in the battery may be, for example, an alkaline
aqueous solution whose main component is KOH and whose specific
weight is 1.2 to 1.4.
[0046] The battery case 110 is made of a metal (e.g., a
nickel-plated steel sheet) and, as shown in FIG. 3, has a battery
container 111 having a rectangular box shape, and an opening
closure member 115 made of a metal (e.g., a nickel-plated steel
sheet) and having a rectangular plate shape. In the battery case
110, a side wall portion 111e (an external wall portion that is
located on the right side in FIG. 3) of the battery container 111
has two penetration holes 111h that penetrate through between an
inside surface 111m and an outside surface 111n. Into each
penetration hole 111h, a negative terminal 140 is fitted with a
packing 145 that is made of an electrically insulating rubber. The
opening closure member 115 is fixed to and thus closes an opening
portion 111g of the battery container 111 by welding the whole
periphery of the opening closure member 115 to an opening end 111f
(see FIG. 3) of the battery container 111 while being placed in
contact with the opening end portion 111f. Therefore, the opening
closure member 115 and the battery container 111 are integrated to
form the battery case 110.
[0047] An electrode body 150 is made up of a plurality of positive
plates 160 and a plurality of negative plates 170 which are
alternately stacked with a separator 180 interposed between each
adjacent two of the positive and negative plates. Of these
components, each positive plate 160 has a positive-electrode filled
portion 160s in which a positive electrode substrate is filled with
a positive electrode active material, and a positive electrode
junction end 160r in which the positive electrode substrate is not
filled with a positive electrode active material. Each positive
plate 160 is disposed so that the positive electrode junction end
portion 160r extends out in a predetermined direction (leftward in
FIG. 3). In Embodiment 1, a foamed nickel substrate is used as the
positive electrode substrate. As the positive electrode active
material, an active material containing nickel hydroxide is
used.
[0048] The negative plate 170 has a negative-electrode filled
portion 170s in which a negative electrode substrate (e.g., a
punched metal plate or the like) is filled with a
hydrogen-absorbing alloy or the like, and a negative electrode
junction end portion 170r in which the negative electrode substrate
170k is not filled with a hydrogen-absorbing alloy or the like.
Each negative plate 170 is disposed so that the negative electrode
junction end portion 170r extends out in a direction (rightward in
FIG. 3) opposite to the direction of the positive electrode
junction end portion 160r. As the separators 180, for example, a
non-woven fabric made of a hydrophilized synthetic fiber may be
used.
[0049] The negative electrode junction end portion 170r of each
negative plate 170 is joined to a rectangular plate-shaped negative
collector member 130 by electron beam welding or the like.
Furthermore, the negative collector member 130 is joined to the
negative terminals 140 by laser welding or the like. Therefore, the
negative terminals 140 and the negative plates 170 are electrically
connected through the negative collector member 130. The positive
electrode junction end portion 160r of each positive plate 160 is
joined to a rectangular plate-shaped positive collector member 120
by electron beam welding or the like. Furthermore, the positive
collector member 120 is joined to the opening closure member 115 by
electron beam welding or the like. Therefore, in the alkaline
storage battery 100 of Embodiment 1, the whole battery case 110,
including the opening closure member 115, acts as a positive
pole.
[0050] Now, the negative terminals 140 and the packings 145 in
Embodiment 1 will be described in detail. The packing 145 of each
negative terminal 140, as shown in FIG. 4, is disposed in intimate
contact with an annular hole periphery portion 111j of the
penetration hole 111h, which is formed in the side wall portion
111e of the battery case 110. The packing 145 has a ring-shaped
flange portion 145b that is positioned outside the battery case
110, and a flange worked portion 145c that is positioned inside the
battery case 110.
[0051] As shown in FIG. 4, each negative terminal 140 has a
cylinder-shape internal cylinder portion 140j that is located
inside the penetration hole 111h with the packing 145 disposed
therebetween, a ring-shape brim portion 140b that is larger in
diameter than the penetration hole 111h and that is located on an
end side of the internal cylinder portion 140j (the right side
thereof in FIG. 4), and a disc-shape squeezed portion 140g that is
larger in diameter than the penetration hole 111h and that is
located on another end side of the internal cylinder portion 140j
(the left side thereof in FIG. 4).
[0052] Among these portions, the squeezed portion 140g, together
with the hole periphery portion 111j of the side wall portion 111e,
clamps and compresses the flange worked portion 145c of the packing
145, on the inside surface 111m side of the side wall portion 111e.
Likewise, the brim portion 140b, together with the hole periphery
portion 111j, clams and compresses the flange portion 145b of the
packing 145, on the outside surface 111n of the side wall portion
111e. Therefore, the penetration hole 111h can be sealed
liquid-tightly.
[0053] In particular, the brim portion 140b of each negative
terminal 140, as shown in FIG. 4, has at or near the middle thereof
in the radial direction an annular seal portion 140c that has an
arch shape in section. The seal portion 140c, as shown in FIG. 5,
has a seal periphery surface 140e, and a seal surface 140f that is
protruded from the seal periphery surface 140e toward the hole
periphery portion 111j. Therefore, in particular, the seal surface
140f can locally compresses the flange portion 145b of the packing
145 to liquid-tightly seal the penetration hole 111h.
[0054] Since the alkaline storage battery 100 of Embodiment 1 uses
an alkaline electrolyte, there occurs a so-called creep phenomenon
in which the alkaline electrolyte in the battery case 110 creeps up
the surfaces of the negative terminals 140. This creep phenomenon
is likely to occur if iron is exposed in surfaces of the negative
terminals. Particularly, if iron is exposed in the seal surface of
a negative terminal, it is likely that the alkaline electrolyte
will leak out along the surface of the negative terminal due to the
creep phenomenon of the alkaline electrolyte.
[0055] However, in Embodiment 1, although each negative terminal
140, including the seal portion 140c, is formed by the press
molding (e.g., deep draw molding) of a metal sheet material (SPCE
in Embodiment 1) that contains iron as a main component, the
surfaces of the negative terminal 140 that includes the seal
surface 140f are molded by nickel plating layers 141 provided after
the press molding (e.g., deep draw molding), as shown in FIG. 5.
Therefore, the exposure of iron in the surfaces of each negative
terminal 140 can be prevented, so that the creep phenomenon of the
alkaline electrolyte on the negative terminals 140 can be
restrained. In particular, since the exposure of iron in the seal
surface 140f can be prevented, the leakage of the alkaline
electrolyte to the outside along the surfaces of the negative
terminals 140 can be particularly restrained.
[0056] When the seal portion is formed by press-molding a metal
sheet material, the whole seal surface or a portion thereof
sometimes is molded without contacting the die. In such a case, the
surface roughness of the seal surface increases (the surface
becomes rough), the liquid tightness for the electrolyte solution
between the seal surface and the packing sometimes becomes
insufficient. When the negative terminals are formed by deep draw
molding, the seal surfaces of seal portions are prone to become
rough.
[0057] In contrast, the alkaline storage battery of Embodiment 1
was actually formed by performing the press molding (e.g., deep
draw molding) of a negative terminal substrate 14 (a negative
terminal substrate before being provided with a nickel plating
layer 141; see FIG. 6), and then performing a surface roughness
reducing process through pressurization surface correction on a
protruded surface 14f of the negative terminal substrate 14 (a
surface that is later coated with a nickel plating layer 141 that
forms the seal surface 140f). Due to this process, the surface
roughness of the protruded surface 14f was made small.
[0058] Therefore, when the surfaces of the negative terminal
substrate 14 are provided with the nickel plating layer 141 so as
to form the negative terminal 140, the surface roughness Ry of the
seal surface 140f formed by the nickel plating layer 141 that coats
the protruded surface 14f was successfully reduced to about 3 .mu.m
(an average value from thirty negative terminals 140). Due to this,
the liquid tightness for the alkaline electrolyte becomes good
between the seal surface 140f and the packing 145, so that the
leakage of the alkaline electrolyte to the outside along the
surface of the negative terminal 140 can be restrained.
[0059] In this embodiment, thirty negative terminals 140 according
to Embodiment 1 were prepared, and the surface roughness Ry of the
seal surface 140f of each negative terminal 140 was measured, and
an average value therefrom was calculated. Thirty negative
terminals 240 to 540 according to each of Embodiments 2 to 5 were
prepared, and an average value of the surface roughness Ry of the
seal surface from each thirty terminals was calculated as in the
negative terminals 140 according to Embodiment 1. Results are shown
by ".box-solid." (solid square) in FIG. 11. FIG. 11 further shows
the maximum values of the surface roughness Ry of the seal surfaces
in Embodiments 1 to 5 and Comparative Example 1 by
".tangle-solidup." (solid triangle).
[0060] The alkaline storage battery 100 of Embodiment 1 is produced
as follows. Firstly, a plurality of positive plate 160 and a
plurality of negative plates 170 are stacked alternately with a
separator 180 disposed between every two plates, and the stack was
pressurized and shaped so as to make an electrode body 150. Next,
the positive plate 160 of the electrode body 150 and the positive
collector member 120 are welded by electron beam welding, and the
negative plates 170 and the negative collector member 130 are
welding by electron beam welding.
[0061] Separately from this, a negative terminal substrate 14 (see
FIG. 6) is produced. Concretely, in an experiment, a deep
drawing-purpose cold-rolled steel sheet (e.g., SPCE) was prepared,
and was subjected to deep draw molding through the use of
predetermined dies to provide a negative terminal substrate 14 as
shown in FIG. 6. The negative terminal substrate 14 has a
shaft-like portion 14k having a bottomed cylinder shape, a disc
ring-shape brim portion 14b provided at a base end (a lower end in
FIG. 6) of the shaft-like portion 14k, and a pair of rectangular
platy connecting portions 14d that are provided radially outward of
the brim portion 14b.
[0062] Among these portions, the shaft-like portion 14k has an
outside diameter that allows the shaft-like portion 14k to be
inserted into the penetration hole 111h of the side wall portion
111e of the battery container 111. The brim portion 14b has an
outside diameter that is larger than the diameter of the
penetration hole 111h. The brim portion 14b has, at or near the
middle in the radial direction, an annular curved portion 14c
having an arch shape in section. The annular curved portion 14c has
a protruded periphery surface 14e, and a protruded surface 14f that
is protruded from the annular curved portion 14c toward the side of
the distal end of the shaft-like portion 14k (upward in FIG. 6). In
an experiment, due to the deep drawing molding, the protruded
surface 14f had an increased surface roughness.
[0063] Next, in the working experiment, the protruded surface 14f
of the negative terminal substrate 14 was subjected to the surface
roughness reducing process through pressurization surface
correction (hereinafter, referred to also as "surface beating").
Concretely, as shown in FIG. 7, the annular curved portion 14c of
the negative terminal substrate 14 was disposed between a first
correction die 21 and a second correction die 22. Next, by
pressurizing the first correction die 21, the protruded surface 14f
was pressed against a contact surface 22b of the second correction
die 22 to perform surface correction. Due to this, the surface
roughness of the protruded surface 14f was successfully made
small.
[0064] After that, the surface of the negative terminal substrate
14 that includes the protruded surface 14f was subjected to
non-gloss electrolytic nickel plating. This provided a negative
terminal member 140A as shown in FIG. 8 in which the surface
including the seal surface 140f was formed by the nickel plating
layer 141 provided after the deep draw molding. This negative
terminal member 140A had a bottomed cylinder-shape shaft-like
portion 140k, and a disc ring-shape brim portion 140b provided on
the base end of the shaft-like portion 140k (on the right side
thereof in FIG. 8). The brim portion 140b had, at or near the
middle in the radial direction, an annular seal portion 140c having
an arch shape in section. This seal portion 140c had a seal
periphery surface 140e, and a seal surface 140f protruded from the
seal periphery surface 140e toward the side of the distal end of
the shaft-like portion 140k (leftward in FIG. 8).
[0065] In Embodiment 1, before the nickel plating layer 141 was
formed, the surface roughness of the protruded surface 14f was
reduced by surface beating. Therefore, the average value of the
surface roughness Ry of the seal surface 140f was made as small as
about 3 .mu.m. Furthermore, as shown in FIG. 11, the maximum value
of the surface roughness Ry in Embodiment 1 was about 7 .mu.m. The
results indicate that Embodiment 1 achieved not merely a small
average value of the surface roughness Ry of the seal surface 140f,
but also a small dispersion in the surface roughness Ry.
Incidentally, in Embodiment 1, the protruded surface 14f of the
negative terminal substrate 14 corresponds to a coated surface.
[0066] Next, as shown in FIG. 4, the negative terminals 140 were
fastened to the hole periphery portions 111j of the side wall
portion 111e of the battery container 111. Concretely, after the
packing 145 was attached to one of the penetration holes 111h of
the side wall portion 111e, the negative terminal 140k of a
negative terminal member 140A was inserted from outside the battery
container 111 into the battery container 111 through the
penetration hole 111h. Next, fluid pressure was applied to the
cylindrical interior space of the shaft-like portion 140k so that a
distal end side portion (a left side portion in FIG. 4) of the
negative terminal 140k expanded radially outward. Then, the
negative terminal 140k was compressed in the axial direction
(rightward in FIG. 4) to form the squeezed portion 140g. Therefore,
the negative terminal 140 was fastened, via the packing 145, to the
hole periphery portion 111j of the side wall portion 111e of the
battery container 111.
[0067] At this time, as shown in FIG. 4, the squeezed portion 140g
of the negative terminal 140, together with the hole periphery
portion 111j, clamps and compresses the flange worked portion 145c
of the packing 145 on the side of the inside surface 111m of the
side wall portion 111e. Furthermore the brim portion 140b, together
with the hole periphery portion 111j, clamps and compresses the
flange portion 145b of the packing 145 on the side of the outside
surface 111n of the side wall portion 111e. In Embodiment 1, in
particular, the seal surface 140f can locally compress the flange
portion 145b of the packing 145. Therefore, the penetration hole
111h can be sealed liquid-tightly.
[0068] Next, the positive collector member 120 joined to the
positive plate 160 of the electrode body 150 was joined to the
inside surface 115b of the opening closure member 115 by electron
beam welding. Next, this joined unit was inserted from the negative
collector member 130 side into the battery container 111 through
the opening portion 111g. At this time, the battery container 111
was closed with the opening closure member 115. After that, by
laser irradiation from outside, the opening closure member 115 and
the battery container 111 were joined to seal the battery container
111. Next, laser was irradiated from outside the battery container
111 toward the squeezed portion 140g of the negative terminal 140
to join the squeezed portion 140g and the negative collector member
130. Then, the electrolyte solution was introduced through an inlet
opening 111k located in a ceiling portion 111a of the battery
container 111, and the safety valve 113 was attached to close the
inlet opening 111k. After that, a predetermined process, including
initial charging and the like, was performed to complete the
alkaline storage battery 100.
[0069] (Embodiment 2) An alkaline storage battery 200 of Embodiment
2 is different from the alkaline storage battery 100 of Embodiment
1 merely in the negative terminals, while other features and the
like remain the same. Concretely, as shown in FIG. 1 (FIG. 8),
instead of the negative terminals 140 (the negative terminal
members 140A) used in Embodiment 1, negative terminals 240
(negative terminal members 240A) were used in Embodiment 2.
[0070] Specifically, in Embodiment 1, in the production of the
negative terminal members 140A, the protruded surface 14f of the
negative terminal substrate 14 was subjected to the surface
roughness reducing process (surface beating) through pressurization
surface correction. Concretely, as shown in FIG. 7, the surface
roughness of the protruded surface 14f was reduced by pressing the
protruded surface 14f against the contact surface 22b of the second
correction die 22.
[0071] On the other hand, in Embodiment 2, in the production of
negative terminal members 240A (negative terminals 240 before being
attached to the battery), the surface roughness of the protruded
surface 14f was reduced by subjecting the negative terminal
substrate 14 to centrifugal barrel grinding. In other features and
the like, Embodiment 2 was substantially the same as Embodiment 1.
The negative terminal member 240A having a nickel plating layer 141
as shown in FIG. 8 was produced. Due to this, the average value of
the surface roughness Ry of the seal surface 240f of the negative
terminal 240 was made about 2 .mu.m. Furthermore, as shown in FIG.
11, the maximum value of the surface roughness Ry in Embodiment 2
was about 4 .mu.m. The results indicate that Embodiment 2 achieved
not merely a small average value of the surface roughness Ry of the
seal surface 240f but also a small dispersion in the value of the
surface roughness Ry.
[0072] (Embodiment 3) An alkaline storage battery 300 of Embodiment
3 is different from the alkaline storage battery 100 of Embodiment
1 merely in the negative terminals, while other features and the
like remain the same Concretely, as shown in FIG. 1 (FIG. 8),
instead of the negative terminals 140 (the negative terminal
members 140A) used in Embodiment 1, negative terminals 340
(negative terminal members 340A) were used in Embodiment 3.
[0073] Specifically, in Embodiment 1, in the production of the
negative terminal members 140A, the surface roughness of the
protruded surface 14f of the negative terminal substrate 14 was
reduced by subjecting the protruded surface 14f to the surface
roughness reducing process through pressurization surface
correction. On the other hand, in Embodiment 3, during the
production of negative terminal members 340A, the surface roughness
reducing process was not performed on the negative terminal
substrate 14. That is, after the negative terminal substrate 14 was
formed by deep draw molding, nickel plating was performed without
performing the surface roughness reducing process on the protruded
surface 14f and the like. In other features and the like,
Embodiment 3 was substantially the same as Embodiment 1. The
negative terminal member 340A having a nickel plating layer 141 as
shown in FIG. 8 was produced.
[0074] Due to this, the average value of the surface roughness Ry
of the seal surface 340f of the negative terminal 340 was made
about 4.5 .mu.m. Furthermore, as shown in FIG. 11, the maximum
value of the surface roughness Ry in Embodiment 3 was about 8
.mu.m. The results indicate that Embodiment 3 achieved not merely a
small average value of the surface roughness Ry of the seal surface
340f but also a small dispersion in the value of the surface
roughness Ry.
[0075] (Embodiment 4) An alkaline storage battery 400 of Embodiment
4 is different from the alkaline storage battery 100 of Embodiment
1 merely in the negative terminals, while other features and the
like remain the same. Concretely, as shown in FIG. 1 (FIG. 9),
instead of the negative terminals 140 (the negative terminal
members 140A) used in Embodiment 1, negative terminals 440
(negative terminal members 440A) were used in Embodiment 4.
[0076] Specifically, in Embodiment 1, the negative terminal
substrate 14 was produced through the use of a deep drawing-purpose
cold-rolled steel sheet (SPCE). On the other hand, in Embodiment 4,
a negative terminal substrate 14 was produced through the use of a
nickel-plated steel sheet obtained by plating the surface of the
SPCE with nickel.
[0077] Furthermore, in Embodiment 1, the negative terminal member
140A was produced by performing nickel plating after performing the
surface roughness reducing process on the protruded surface 14f of
the negative terminal substrate 14. On the other hand, in
Embodiment 4, the negative terminal member 440A as shown in FIG. 9
was produced without performing nickel plating after performing the
surface roughness reducing process on the protruded surface 14f of
the negative terminal substrate 14 as in Embodiment 1. Therefore,
the negative terminal 440 of Embodiment 4 was different from the
negative terminal 140 of Embodiment 1, in that iron was exposed in
the seal surface 440f.
[0078] The average value of the surface roughness Ry regarding the
seal surface 440f of the negative terminal 440 was about 2.5 .mu.m.
Furthermore, as shown in FIG. 11, the maximum value of the surface
roughness Ry in Embodiment 4 was about 5 .mu.m. The results
indicate that Embodiment 4 achieved not merely a small average
value of the surface roughness Ry of the seal surface 440f but also
a small dispersion in the value of the surface roughness Ry.
[0079] (Embodiment 5) An alkaline storage battery 500 of Embodiment
5 is different from the alkaline storage battery 100 of Embodiment
1 merely in the negative terminals, while other features and the
like remain the same. Concretely, as shown in FIG. 1 (FIG. 9),
instead of the negative terminals 140 (the negative terminal
members 140A) used in Embodiment 1, negative terminals 540
(negative terminal members 540A) were used in Embodiment 5.
[0080] Specifically, in Embodiment 1, the negative terminal
substrate 14 was produced through the use of a deep drawing-purpose
cold-rolled steel sheet (SPCE). On the other hand, in Embodiment 5,
a negative terminal substrate 14 was produced through the use of a
nickel-plated steel sheet obtained by plating the surface of the
SPCE with nickel. Furthermore, in Embodiment 1, the protruded
surface 14f of the negative terminal substrate 14 was subject to
surface beating. On the other hand, in Embodiment 5, the negative
terminal substrate 14 was subjected to centrifugal barrel
grinding.
[0081] Furthermore, in Embodiment 1, the negative terminal member
140A was produced by performing nickel plating after performing the
surface roughness reducing process on the protruded surface 14f of
the negative terminal substrate 14. On the other hand, in
Embodiment 5, the negative terminal member 540A as shown in FIG. 9
was produced without performing nickel plating after performing the
centrifugal barrel grinding on the negative terminal substrate 14.
Therefore, the negative terminal 540 of Embodiment 5 was different
from the negative terminal 140 of Embodiment 1, in that iron was
exposed in the seal surface 540f.
[0082] The average value of the surface roughness Ry regarding the
seal surface 540f of the negative terminal 540 was about 2 .mu.m.
Furthermore, as shown in FIG. 11, the maximum value of the surface
roughness Ry in Embodiment 5 was about 4.5 .mu.m. The results
indicate that Embodiment 5 achieved not merely a small average
value of the surface roughness Ry of the seal surface 540f but also
a small dispersion in the value of the surface roughness Ry.
[0083] (Comparative Example 1) An alkaline storage battery of
Comparative Example 1 is different from the alkaline storage
battery 400 of Embodiment 4 merely in the negative terminals, while
other features and the like remain the same. Concretely, in
Embodiment 4, in the production of the negative terminal members
440A, the protruded surface 14f of the negative terminal substrate
14 was subjected to the surface roughness reducing process.
[0084] On the other hand, in Comparative Example 1, in the
production of negative terminal members, the negative terminal
substrate 14 was not subjected to the surface roughness reducing
process. That is, after the negative terminal substrate 14 was
formed by the deep draw molding of a nickel-plated steel sheet, the
surface roughness reducing process was not performed on the
protruded surface 14f or the like, but the obtained negative
terminal substrate was directly used as a negative terminal member
Therefore, in Comparative Example 1, the average value of the
surface roughness Ry regarding the seal surface of the negative
terminal was about 17 .mu.m. Furthermore, in the seal surface, the
nickel plating layer had cracks, and partially ion was exposed.
Still further, as shown in FIG. 11, in Comparative Example 1, the
maximum value of the surface roughness Ry was as large as about 30
.mu.m. The results indicate that Comparative Example 1 had not
merely a larger value of the surface roughness Ry regarding the
seal surface of the negative terminal, but also a larger dispersion
in the value of the surface roughness Ry than Embodiments 1 to
5.
[0085] (Leak Test) A leak test was performed on the alkaline
storage batteries 100 to 500 in accordance with Embodiments 1 to 5
and the alkaline storage battery in accordance with Comparative
Example 1 were subjected to a leak test. Concretely, the alkaline
storage battery 100 in accordance with Embodiment 1 was charged to
an SOC of 60%. After that, the creep phenomenon of the alkaline
electrolyte was accelerated by leaving the alkaline storage battery
100 in a chamber set at a temperature of 60.degree. C. and a
humidity of 75%, for 83 days. Then, after the alkaline storage
battery 100 was taken out of the chamber, a negative terminal
140-side portion of the alkaline storage battery 100 was dipped in
100 mL of pure water at 60.degree. C.
[0086] Then, using an ICP analysis device, the concentration (mg/L)
potassium ions contained in 100 mL of pure water was measured.
After that, on the basis of the measured concentration (mg/L) of
potassium ions, the amount of leakage of the alkaline electrolyte
(.mu.L) was calculated. In this embodiment, thirty alkaline storage
batteries 100 of Example 1 were prepared, and the leak test was
performed on each of the alkaline storage devices 100. For the
alkaline storage devices 100, the amounts (.mu.L) of leakage of the
alkaline electrolyte were calculated and an average value thereof
(referred to as "average amount of leakage") was obtained.
[0087] Thirty alkaline storage batteries in accordance with each of
Embodiments 2 to 5 and Comparative Example 1 were prepared, and the
leak test was performed on each battery similarly to the alkaline
battery cell 100 in accordance with Embodiment 1, and an average
amount of leakage of the alkaline electrolyte was calculated.
Results are shown in FIG, 10. In FIG. 10, the average leak amount
of the alkaline storage battery in accordance with Comparative
Example 1 was set as a reference (100%), and the average leak
amounts of the alkaline storage batteries of Embodiments 1 to 4 are
shown in terms of the proportion (%) to the average leak amount of
the alkaline storage battery in accordance with Comparative Example
1.
[0088] Firstly, the results of the alkaline storage batteries 400,
500 of Embodiments 4, 5 and the alkaline storage battery in
accordance with Comparative Example 1 will be compared. These
alkaline storage batteries were in the relationship in which the
materials of the negative terminals were the same (they were all
made of a nickel-plated steel sheet) and there was difference only
in the surface roughness reducing process of the seal surface of
the negative terminals. Concretely, as for the alkaline storage
batteries of Comparative Example 1, the seal surfaces of the
negative terminals were not subjected to the surface roughness
reducing process at all after the deep draw molding, and the
average value of the surface roughness Ry of the seal surfaces was
about 17 .mu.m. In contrast, as for the alkaline storage batteries
400 of Embodiment 4, the seal surfaces of the negative terminals
were subjected to surface beating, and the average value of the
surface roughness Ry of the seal surfaces was about 2.5 .mu.m. As
for the alkaline storage batteries 500 of Embodiment 5, the
surfaces of the negative terminals, including the seal surfaces,
were subjected to centrifugal barrel grinding, and the average
value of the surface roughness Ry of the seal surfaces was about 2
.mu.m.
[0089] As for the alkaline storage batteries 400 of Embodiment 4,
the average leak amount was about 55%. That is, in comparison with
the alkaline storage batteries of Comparative Example 1, the leak
amount was reduced by about 45%. As for the alkaline storage
batteries 500 of Embodiment 5, the average leak amount was about
28%. That is, in comparison with the alkaline storage batteries of
Comparative Example 1, the leak amount was reduced by as much as
about 72%. From these results, it can be said that the leakage of
the alkaline electrolyte to the outside along the surfaces of the
negative terminals can be restrained by performing surface beating
or grinding on the seal surfaces after the negative terminals have
been formed by deep draw molding (after the seal portions have been
formed by press molding). It can be considered that, by performing
surface beating or the grinding on the seal surfaces, the surface
roughness Ry of the seal surfaces was reduced to or below 15 .mu.m
(concretely, the surface roughness Ry was reduced to about 2.5
.mu.m or about 2 .mu.m).
[0090] Next, the results of the alkaline storage batteries 100 to
300 of Embodiments 1 to 3 and the alkaline electrolyte of
Comparative Example 1 will be compared. These alkaline storage
batteries are in a relationship where they are different as to
whether the surfaces of the negative terminals, including the seal
surfaces, were subjected to nickel plating after the negative
terminals were formed by deep draw molding. Concretely, as the
alkaline storage batteries 100 to 300 of Embodiments 1 to 3, nickel
plating was performed after the deep draw molding. However, as for
the alkaline storage batteries of Comparative Example 1, nickel
plating was not performed after the deep draw molding.
[0091] The average leak amounts of the alkaline storage batteries
100 to 300 of Embodiment 1 to 3 were about 5%, about 2% and about
2%, respectively That is, in comparison with the alkaline storage
batteries of Comparative Example 1, the leak amount was reduced by
as much as 95% or more. From these results, it can be said that the
leakage of the alkaline electrolyte to the outside along the
surfaces of the negative terminals can be restrained by performing
nickel plating after the deep draw molding so that the seal
surfaces are formed by the nickel plating layer. This is considered
to be because although the negative terminal substrate was formed
of SPCE, the following coating of the seal surfaces and the like
with nickel plating prevented exposure of iron in the seal surfaces
and the like. It is considered that this restrained the creep
phenomenon of the alkaline electrolyte on the seal surfaces and the
like.
[0092] In the alkaline storage batteries of Comparative Example 1,
the negative terminals were formed of a nickel-plated steel sheet,
and an extremely increased leak amount resulted in comparison with
the alkaline storage batteries 100 and the like whose negative
terminals were subjected to nickel plating after the deep draw
molding thereof. This is considered to be because when the
nickel-plated steel sheet was deep-draw-molded, cracks and the like
were formed so that iron was exposed in the seal surfaces.
[0093] The average values of the surface roughness Ry of the seal
surfaces of the negative terminals of the alkaline storage
batteries 100 to 300 of Embodiments 1 to 3 were about 3 .mu.m,
about 2 .mu.m and 4.5 .mu.m, respectively. On the other hand, as
for the alkaline storage batteries of Comparative Example 1, the
average value of the surface roughness Ry of the seal surfaces was
about 17 .mu.m. From this, it can be said that by limiting the
surface roughness Ry of the seal surfaces of the negative terminals
to 15 .mu.m or less, the leakage of the alkaline electrolyte to the
outside along the surfaces of the negative terminals can be
restrained.
[0094] While the invention has been described with reference to
Embodiments 1 to 5, the invention is not limited to the foregoing
embodiments. On the contrary, it is apparent that the invention is
applicable with appropriate modifications without departing from
the spirit of the invention. For example, in Embodiments 1 to 5, a
nickel-metal hydride storage battery is used as the alkaline
storage batteries 100 to 500. However, the invention is also
applicable to any alkaline storage battery that incorporates an
alkaline electrolyte.
[0095] Furthermore, Embodiments 1 to 5 have been described in
conjunction with an alkaline storage battery (concretely, a
nickel-metal hydride storage battery) whose battery case 110 is a
positive pole, and which has the negative terminals 140 to 540 as
electrode terminals. However, the invention is also applicable to
an alkaline storage battery of an opposite arrangement in which the
battery case 110 is a negative pole, and positive terminals are
provided as electrode terminals. In this nickel-metal hydride
storage battery, too, the invention is able to appropriately
restrain the leakage of the alkaline electrolyte to the outside
along the surfaces of the positive terminals. Furthermore, the
invention is also applicable to an alkaline storage battery having
positive terminals and negative terminals, that is, the invention
is also able to restrain the leakage of the alkaline electrolyte
along the surfaces of the positive terminals and the negative
terminals.
* * * * *